On the Stellar Populations in NGC 185 and NGC 205 and the Nuclear Star Cluster in NGC 205 from<i>Hubble Space Telescope</i>Observations

Butler, D.; Martínez–Delgado, David

doi:10.1086/429524

Cited by 60 publications

(70 citation statements)

References 68 publications

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“…This value is 0.6 dex higher than the value used by Battinelli & Demers (2005). A difference of ∼0.2 dex is found for NGC147, NGC 185 and NGC 205 by Butler & Martínez-Delgado (2005) who obtained a mean RGB metallicity of −1.11 dex and −1.06, respectively.…”

Section: Appendix B: C/m Versus [Fe/h] Calibrationmentioning

confidence: 53%

The metallicity gradient as a tracer of history and structure: the Magellanic Clouds and M33 galaxies

Cioni¹

2009

A&A

133

154

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Context. The stellar metallicity and its gradient place constraints on the formation and evolution of galaxies. Aims. This is a study of the metallicity gradient of the LMC, SMC and M33 galaxies derived from their asymptotic giant branch (AGB) stars. Methods. The [Fe/H] abundance was derived from the ratio between C-and M-type AGB stars and its variation analysed as a function of galactocentric distance. Galaxy structure parameters were adopted from the literature.Results. The metallicity of the LMC decreases linearly as −0.047± 0.003 dex kpc −1 out to ∼8 kpc from the centre. In the SMC, [Fe/H] has a constant value of ∼−1.25 ± 0.01 dex up to ∼12 kpc. The gradient of the M33 disc, until ∼9 kpc, is −0.078 ± 0.003 dex kpc −1 while the outer disc/halo, out to ∼25 kpc, has [Fe/H] ∼ −1.7 dex. Conclusions. The metallicity of the LMC, as traced by different populations, bears the signature of two major star forming episodes: the first one constituting a thick disc/halo population and the second one a thin disc and bar due to a close encounter with the Milky Way and SMC. The [Fe/H] of the recent episode supports an LMC origin for the Stream. The metallicity of the SMC supports star formation, ∼3 Gyr ago, as triggered by LMC interaction and sustained by the bar in the outer region of the galaxy. The SMC [Fe/H] agrees with the present-day abundance in the Bridge and shows no significant gradient. The metallicity of M33 supports an "insideout" disc formation via accretion of metal poor gas from the interstellar medium.

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Section: Appendix B: C/m Versus [Fe/h] Calibrationmentioning

confidence: 53%

The metallicity gradient as a tracer of history and structure: the Magellanic Clouds and M33 galaxies

Cioni¹

2009

A&A

133

154

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“…In nucleated Local Group galaxies such as NGC 205 and Sagittarius, King models are found to provide accurate representations of the central components (e.g., Djorgovski et al 1992;Butler & Martínez-Delgado 2005;Monaco et al 2005). Nevertheless, for galaxies at the distance of the Virgo Cluster, we are working close to the limits of resolvability, so we caution that our choice of King models to parameterize the central components may not be unique, particularly for faint nuclei in the highest surface brightness galaxies.…”

Section: Parameterization Of the Surface Brightness Profilesmentioning

confidence: 99%

The ACS Virgo Cluster Survey. VIII. The Nuclei of Early‐Type Galaxies

Côté

Piatek

Ferrarese

et al. 2006

ASTROPHYS J SUPPL S

444

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The ACS Virgo Cluster Survey is a Hubble Space Telescope program to obtain high-resolution imaging in widely separated bandpasses ( F475W % g and F850LP % z) for 100 early-type members of the Virgo Cluster, spanning a range of %460 in blue luminosity. We use this large, homogenous data set to examine the innermost structure of these galaxies and to characterize the properties of their compact central nuclei. We present a sharp upward revision in the frequency of nucleation in early-type galaxies brighter than M B % À15 (66% P f n P 82%) and show that groundbased surveys underestimated the number of nuclei due to surface brightness selection effects, limited sensitivity and poor spatial resolution. We speculate that previously reported claims that nucleated dwarfs are more concentrated toward the center of Virgo than their nonnucleated counterparts may be an artifact of these selection effects. There is no clear evidence from the properties of the nuclei, or from the overall incidence of nucleation, for a change at M B $ À17:6, the traditional dividing point between dwarf and giant galaxies. There does, however, appear to be a fundamental transition at M B $ À20:5, in the sense that the brighter, ''core-Sérsic'' galaxies lack resolved (stellar) nuclei. A search for nuclei that may be offset from the photocenters of their host galaxies reveals only five candidates with displacements of more than 0B5, all of which are in dwarf galaxies. In each case, however, the evidence suggests that these ''nuclei'' are, in fact, globular clusters projected close to the galaxy photocenter. Working from a sample of 51 galaxies with prominent nuclei, we find a median half-light radius of hr h i ¼ 4:2 pc, with the sizes of individual nuclei ranging from 62 pc down to 2 pc (i.e., unresolved in our images) in about a half-dozen cases. Excluding these unresolved objects, the nuclei sizes are found to depend on nuclear luminosity according to the relation r h / L 0:50AE0:03 . Because the large majority of nuclei are resolved, we can rule out low-level AGNs as an explanation for the central luminosity excess in almost all cases. On average, the nuclei are %3.5 mag brighter than a typical globular cluster. Based on their broadband colors, the nuclei appear to have old to intermediate age stellar populations. The colors of the nuclei in galaxies fainter than M B % À17:6 are tightly correlated with their luminosities, and less so with the luminosities of their host galaxies, suggesting that their chemical enrichment histories were governed by local or internal factors. Comparing the nuclei to the ''nuclear clusters'' found in late-type spiral galaxies reveals a close match in terms of size, luminosity, and overall frequency. A formation mechanism that is rather insensitive to the detailed properties of the host galaxy properties is required to explain this ubiquity and homogeneity. The mean of the frequency function for the nucleus-to-galaxy luminosity ratio in our nucleated galaxies, hlog i ¼ À2:49 AE 0:09 dex ( ¼ 0:59 AE 0:10), i...

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“…Their distances are well determined, and the properties of their stellar populations have been thoroughly studied (e.g. Mould et al 1983;Davidge 1994Davidge , 2005Lee et al 1993;Grebel 2000;McConnachie 2005;Butler & Martínez-Delgado 2005;Dolphin 2005). NGC 147 is composed of old (90%) and intermediate-age stellar populations (Mould et al 1983;Davidge 2005).…”

Section: Introductionmentioning

confidence: 99%

“…It has been argued that the gas-free M 32 is a stripped spiral (Bekki et al 2001;Graham 2002). NGC 185 and 205 contain neutral hydrogen and molecular gas, dust, and young stars (Baade 1944a,b;Hodge 1963;Lee et al 1993;Butler & Martínez-Delgado 2005;Young & Lo 1997;Sage et al 1998). Both galaxies reveal bright nuclei with a young star-forming region in the first one, and a relatively young star cluster in the other (see e.g.…”

Section: Introductionmentioning

confidence: 99%

“…The most prominent properties of stellar populations, common to NGC 147, 185, and 205, are i) sizable globular cluster systems, where the majority of GCs are old and metalpoor (Da Costa & Mould 1988;van den Bergh 2000;Sharina et al 2006b); ii) the presence of intermediate-age stars (Davidge 2005;Saha et al 1990), planetary nebulae (Richer & McCall 1995;Corradi et al 2005;Gonçalves et al 2006); and iii) similar median metallicities of old stars, [Fe/H] ∼ −0.9 dex (Butler & Martínez-Delgado 2005;Davidge 2005). It is noteworthy that the stellar halo of M 31 at galactocentric distances R ≥ 60 kpc is more metal-poor [Fe/H] = −1.26 ± 0.10 dex (σ = 0.72) (Kalirai et al 2006).…”

Section: Introductionmentioning

confidence: 99%

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Globular cluster content and evolutionary history of NGC 147

Шарина

Davoust

2009

A&A

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Context. Globular clusters are representative of the oldest stellar populations. It is thus essential to have a complete census of these systems in dwarf galaxies, from which more massive galaxies are progressively formed in the hierarchical scenario. Aims. We present the results of spectroscopic observations of eight globular cluster candidates in NGC 147, a satellite dwarf elliptical galaxy of M 31. Our goal is to make a complete inventory of the globular cluster system of this galaxy, determine the properties of their stellar populations, and compare these properties with those of systems of globular clusters in other dwarf galaxies. Methods. The candidates were identified on Canada-France-Hawaii telescope photographic plates. Medium resolution spectra were obtained with the SCORPIO spectrograph at the prime focus of the 6 m telescope of the Russian Academy of Sciences. They were analyzed using predictions of stellar population synthesis models. Results. We were able to confirm the nature of all eight candidates, three of which (GC5, GC7, and GC10) are indeed globular clusters, and to estimate evolutionary parameters for the two brightest ones and for Hodge II. The bright clusters GC5 and GC7 appear to have metallicities ([Z/H] ∼ −1.5 ÷ −1.8) that are lower than the oldest stars in the galaxy. The fainter GC Hodge II has a metallicity [Z/H] = −1.1, similar to that of the oldest stars in the galaxy. The clusters GC5 and GC7 have low alpha-element abundance ratios. The mean age of the globular clusters in NGC 147 is 9 ± 1 Gyr. We also measured the radial velocities of Hodge II and IV, and derived a mass of NGC 147 in good agreement with the value from the literature. The frequency, S n = 6.4, and mass fraction, T = 14 of globular clusters in NGC 147 appear to be higher than those for NGC 185 and 205. Conclusions. Our results indicate that the bright clusters GC5, GC7, and Hodge III formed in the main star-forming period ∼8−10 Gyr ago, while the fainter clusters Hodge I and II formed together with the second generation of field stars.

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On the Stellar Populations in NGC 185 and NGC 205 and the Nuclear Star Cluster in NGC 205 fromHubble Space TelescopeObservations

Cited by 60 publications

References 68 publications

The metallicity gradient as a tracer of history and structure: the Magellanic Clouds and M33 galaxies

The metallicity gradient as a tracer of history and structure: the Magellanic Clouds and M33 galaxies

The ACS Virgo Cluster Survey. VIII. The Nuclei of Early‐Type Galaxies

Globular cluster content and evolutionary history of NGC 147

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